主要原理是利用webpack插件webpack-theme-color-replacer提取相关颜色css然后根据配置动态生成替换的css
具体实现步骤如下：
1.添加webpack插件，新建文件webpack/themePlugin.js
const ThemeColorReplacer = require('webpack-theme-color-replacer')
const forElementUI = require('webpack-theme-color-replacer/forElementUI')
const config = require('../src/config/appConfig')
module.exports = new ThemeColorReplacer({

fileName: 'css/theme-colors.[contenthash:8].css',

matchColors: [

...forElementUI.getElementUISeries(config.themeColor), //element-ui主色系列

// '#0cdd3a', //自定义颜色

],

changeSelector: forElementUI.changeSelector,

isJsUgly: process.env.NODE_ENV !== 'development',

// injectCss: false,

// resolveCss(resultCss) { // optional. Resolve result css code as you wish.

//
return resultCss + youCssCode

// }
})
const ThemeColorReplacer = require('webpack-theme-color-replacer')
const forElementUI = require('webpack-theme-color-replacer/forElementUI')
const config = require('../src/config/appConfig')
module.exports = new ThemeColorReplacer({

fileName: 'css/theme-colors.[contenthash:8].css',

matchColors: [

...forElementUI.getElementUISeries(config.themeColor), //element-ui主色系列

// '#0cdd3a', //自定义颜色

],

changeSelector: forElementUI.changeSelector,

isJsUgly: process.env.NODE_ENV !== 'development',

// injectCss: false,

// resolveCss(resultCss) { // optional. Resolve result css code as you wish.

//
return resultCss + youCssCode

// }
})matchColors数组中可配置多个自定义要替换的主题色
2.在vue.config.js中添加这个插件
const themePlugin=require('./webpack/themePlugin');
module.exports = {
configureWebpack: {

plugins: [

themePlugin

]

}
}

const themePlugin=require('./webpack/themePlugin');
module.exports = {
configureWebpack: {

plugins: [

themePlugin

]

}
}
3.新建文件themeColorClient.js
import client from 'webpack-theme-color-replacer/client'
import forElementUI from 'webpack-theme-color-replacer/forElementUI'
import appConfig from '@/config/appConfig'
export let curColor = appConfig.themeColor

// 动态切换主题色
export function changeThemeColor(newColor) {

var options = {

newColors: [...forElementUI.getElementUISeries(newColor)],

}

return client.changer.changeColor(options, Promise)

.then(() => {

curColor = newColor

localStorage.setItem('theme_color', curColor)

});
}

export function initThemeColor() {

const savedColor = localStorage.getItem('theme_color')

if (savedColor) {

curColor = savedColor

changeThemeColor(savedColor)

}
}


import client from 'webpack-theme-color-replacer/client'
import forElementUI from 'webpack-theme-color-replacer/forElementUI'
import appConfig from '@/config/appConfig'
export let curColor = appConfig.themeColor

// 动态切换主题色
export function changeThemeColor(newColor) {

var options = {

newColors: [...forElementUI.getElementUISeries(newColor)],

}

return client.changer.changeColor(options, Promise)

.then(() => {

curColor = newColor

localStorage.setItem('theme_color', curColor)

});
}

export function initThemeColor() {

const savedColor = localStorage.getItem('theme_color')

if (savedColor) {

curColor = savedColor

changeThemeColor(savedColor)

}
}

4.在需要的时候调用 initThemeColor初始化颜色 changeThemeColor改变主题颜色
import { initThemeColor,changeThemeColor } from './utils/themeColorClient'
initThemeColor()
changeThemeColor('#F56C6C')//传入颜色格式应该为十六进制颜色值，'red'类似颜色暂不支持

import { initThemeColor,changeThemeColor } from './utils/themeColorClient'
initThemeColor()
changeThemeColor('#F56C6C')//传入颜色格式应该为十六进制颜色值，'red'类似颜色暂不支持
具体细节请参考https://github.com/hzsrc/vue-element-ui-scaffold-webpack4https://github.com/hzsrc/vue-element-ui-scaffold-webpack4